The overall goals of this proposal are to identify the early manifestations of lung disease among the WTC workers and volunteers, as well as investigate their risk factors. To accomplish this, we will perform standardized and computer-assisted readings of all the chest CT scans performed at Mount Sinai Medical Center on these workers since January 2003, assess the findings in a systematic way, evaluate the correlation of findings with clinical, functional, and exposure indicators, and develop a protocol for continued radiological surveillance of this cohort. In order to validate the findings from the chest CT scans obtained from 2002-2011 (2870 studies in 1710 workers), we will prospectively perform paired inspiratory-expiratory, low- dose, gated CT scans and spirometry on a set of 800 participants over the 4 years of the grant, to determine the prevalence of lung cancer, emphysema, fibrotic and Interstitial lung disease, small airways disease (including air trapping). We will select individuals for whom there would not be a clinical indication to test some of the secondary hypotheses, to update a previous study, and to allow case-control studies with the retrospective cases (most of whom had respiratory symptoms, spirometric abnormalities, or chest radiographic abnormalities, or any combination thereof).